Methods for plasma-arc Welding of metals using the direct constricted-arc welding technique are in widespread use currently, wherein metal is fused with a plasma jet (cf. U.S. Pat. No. 4,791,268, IPC B23K 9/00, 1988; SU #1,683,927, IPC B23K 10/00, 1991). Extensively used nowadays are also methods for welding metals with a direct constricted arc stricken between the plasmatron electrodes and the workpiece (cf. SU #880,6,54, IPC B23K 10/02, 1981; the textbook "Microplasma-arc welding" ed. by B. Ye. Patton, Ukraine, Kiev, "Naukova dumlka" publishers, 1979, pp.19-21 (in Russian). The methods mentioned above provide for establishing a plasma jet by constricting an arc discharge with an inert gas to obtain quality welded joints. However, provision of an external inert-gas source involves some operational inconveniences in carrying said method into effect, while high production cost of the inert gas and considerable expenses for recharging gas bottles impose substantial limitation on practical applicability of the aforementioned method of plasma-arc welding. In addition, handling easily inflammable metals involves using not only a plasma-producer gas but also a shielding gas (cf. SU #1,680,463, IPC B23J 10/02, 1991).
Known in the present-state welding practice are plasma-arc welding torches (plasmatrons), wherein used for establishing a plasma jet is vapor fed from a special vapor generator or generated in the welding torch itself by evaporating the fluid by virtue of the heat released on the electrodes (cf. PCT RU Application #93/00053 published Sep. 1, 1994 under # WO/94/19139). The latter torch is most economic and simple in operation, though its use in welding is difficult due to intense metal oxidizing caused by the presence of vapor and molecular and atomic oxygen in the plasma jet.